Abstract: The aim of this paper was to investigate the properties of Cu40ZnTi for the purpose of developing a new
high-strength, lead-free brass by powder metallurgy. The effect of Ti addition on precipitation hardening
behavior of Cu40Zn (denoted as BS40) brass was studied with respect to mechanical properties and
microstructures. BS40 and Cu40Zn 1.0 wt.%Ti (denoted as BS40-A) brass powders were prepared by
water atomization process, and b phase was retained in the raw powders predominately. The BS40 powder
and Ti powder were elementally mixed to prepare Cu40Zn + 0.5 wt.%Ti (denoted as BS40-B) and
Cu40Zn + 1.0 wt.%Ti (denoted as BS40-C) premixed powders. The alloy powders and premixed powders
were solidified at 1053 K for 600 s by spark plasma sintering (SPS) and extruded subsequently. It was
observed that Cu2ZnTi intermetallic compound (IMC) and CuZnTi metastable phase resulted from the
reaction between Ti and CuZn showed distinct grain refinement effect on extruded Cu40Zn brass. Thus,
the excellent strengthening effect processes by precipitation hardening and deform working was
obtained, which responding to an yield strength of 345 MPa, and a ultimate tensile strength of
597 MPa, showed 65.9% and 30.4% higher than that of extruded Cu40Zn brass, respectively.
Abstract:
Zirconia (yttria)–alumina ceramic nanocomposites were fabricated from different powders by spark plasma sintering (SPS). One powder was a commercially available nanocomposite powder TZP-3Y20A, consisting of 3 mol% yttria-stabilized zirconia (3-YSZ) reinforced with 20 wt% alumina, and the other, used as a comparison, was a conventional mechanically mixed powder 3YSZ-20A, a blend made of 3 mol% yttria-stabilized zirconia powder ZrO2 (3Y) and 20 wt% α-alumina powder. The effect of the sintering temperature on the densification, the sintering behavior, the mechanical properties and the microstructure of the composites was investigated. The results showed that the density increased with increasing sintering temperature, and thus, the mechanical properties were strengthened because of the increased densification. The nanocomposite powder TZP-3Y20A was easily sintered, and good mechanical properties were achieved as compared with the powder from the conventional mechanically mixed method, the maximum flexural strength and fracture toughness of which were 967 MPa and 5.27 MPa m1/2, respectively.
Abstract: The microstructure, mechanical properties and fracture behavior of a high strength, novel copper alloy
BS40CrFeSn were studied, which are prepared by hot pressing, spark plasma sintering and casting, respectively.
Duplex / phase structures are formed by using the -phase raw powder, resulted from the
phase transformation of the parent -phase experienced different thermal histories combined with the
extrusion deformation. The ultrafine metastable phase particles precipitated during powder pressing and
consequent extrusion, serving as precipitation hardening which could elevate the mechanical strength
distinctly. In the sample sintered at 1053 K, CrFe rich metastable phase coalesces and resulted in the
formation of spherical coarser particles, the ductility elevated obviously.
Abstract: Phase transformation and precipitation hardening
behavior of the water atomized copper alloy powder
was studied by aging treatment, to develop high strength
Cu–40Zn–X (X: Cr, Fe, Sn) alloys by powder metallurgy
process. Super-saturated solid solution elements of Cr and
Fe are formed in the brass matrix, and single b phase was
retained in the raw powder after water atomization. Solid
solubility of Cr and Fe decreased with increase of aging
temperature, and phase transformation evolved from single
b phase to a ? b duplex phase structure after aged at the
elevated temperature of 773 K and over. It was clarified
that Cr showed higher precipitation potential than Fe in the
brass matrix. The hardness depended strongly upon solid
solubility of Cr and Fe, and upon phase transformation
Abstract: Yttria-stabilized tetragonal zirconia/20 wt% alumina (TZP-3Y20A) composites were fabricated by spark plasma sintering at various sintering temperatures over the range of 1000—1400°C. Hydroxyapatite (HA) additive was added in volume fractions of 10—50% in order to increase the biocompatibility of the composite. The densification behavior of the TZP-3Y20A composite and that of the composites with HA were investigated. In the case of TZP-3Y20A composites, the density increases steadily with temperature and reaches a maximum value of 97.8% of the theoretical density at 1400°C. The solution interface formed between zirconia (ZrO2) and alumina (Al 2O3) strengthens the bond between ZrO2 and Al 2O3 grains and facilitates densification. In the case of TZP-3Y20A/HA composites, sintering at 1400°C led to the formation of tricalcium phosphate in the samples, which resulted from the decomposition of HA due to its limited thermal stability at high temperature; no reaction was observed between ZrO2 and HA. The addition of HA imposes a barrier effect on the diffusion between ZrO2 and Al2O3 grains, thus limiting the grain growth of ZrO2 and Al2O 3.
Abstract: TZP-3Y20A/HA composites with addition of different volume fraction of hydroxyapatite (HA) were fabricated successfully using spark plasma sintering (SPS). The densification behavior and mechanical properties of composites are investigated as a function of sintering temperature and HA content respectively. The density of TZP-3Y20A composite increases steadily with temperature and a maximum value of 97.8% is obtained after sintering at 1400ï‚°C. Sintering the TZP-3Y20A/HA composites at 1400ï‚°C led to the decomposition of HA in the samples. Flexural strength, fracture toughness and Vickers hardness values increase with increasing sintering temperature, show decrease trend with increasing of HA content at the same temperature. They compared well with densities obtained at different sintering temperature. The maximum flexural strength, fracture toughness and Vickers hardness of 967.1 MPa, 5.27 MPam1/2 and 13.26 GPa were achieved for TZP-3Y20A composite respectively. Flexural strength, fracture toughness and Vickers hardness values of TZP-3Y20A/HA composite fell within the value range of dense HA and of TZP-3Y20A composite.
Abstract: The sintering behaviors and resulting properties of hydroxyapatite (HA) were studied by employing Spark plasma sintering (SPS) process. An As-received HA powder was sintered and the sintering pressure was set as 22.3MPa, 44.6MPa and 66.9MPa respectively. At each pressure, the HA powder was sintered at different temperatures ranging from 800°C to 1000°C with a duration time of 8 minutes. The results showed that the HAp compact was rapidly densified to near theoretical density with the relative density of 99.1%. The samples sintered at 44.6MPa possess higher flexural strength and Young's modulus than those at 22.3MPa. The flexural strength and Young’s modulus achieved a maximum value of 123.2MPa and 75.2GPa respectively when the samples were sintered at 950°C and at pressure of 44.6MPa. The external pressure accelerates the densification behaviors and overlade external pressure at 66.9MPa resulted in high residual stresses and thus deteriorated the mechanical properties. The XRD results indicated there was no decomposition of HA sintered at elevated temperature up to 1000°C. The drop of mechanical properties was considered as the result of grain growth and hence residual stress induced microcracks.
